The object of this study is the assessment of familial aggregation of outcomes measuring periodontal disease in a population-based family study in the Piedmont area of North Carolina. The study sample includes members of nuclear families ascertained through individuals studied as part of a population-based epidemiologic study of elder North Carolinians, regardless of periodontal status. Clinical, behavioral, and immunological measures were obtained for study. In a subset of these persons, who were found to have severe periodontal disease, extended family structures were sampled. Analyses to date provide evidence of significant levels of familial aggregation.